Neonicotinoids are widely used systemic insecticides that have been associated with spider mite outbreaks on diverse plants. These insecticides have complex effects on plant physiology, which have been speculated to drive enhanced performance of spider mites. We used RNA-Seq to explore how neonicotinoids modify gene expression in soybean thereby lowering plant resistance. We exposed soybean (Glycine max L.) to two neonicotinoid insecticides, thiamethoxam applied to seeds and imidacloprid applied as a soil drench, and we exposed a subset of these plants to spider mites (Tetranychus cinnabarinus). Applications of both insecticides downregulated genes involved in plant—pathogen interactions, phytohormone pathways, phenylpropanoid pathway, and cell wall biosynthesis. These effects were especially pronounced in plants exposed to thiamethoxam. Introduction of spider mites restored induction of genes in these pathways in plants treated with imidacloprid, while expression of genes involved in phenylpropanoid synthesis, in particular, remained downregulated in thiamethoxam-treated plants. Our outcomes indicate that both insecticides suppress genes in pathways relevant to plant–arthropod interactions, and suppression of genes involved in cell wall synthesis may explain lower plant resistance to spider mites, cell-content feeders. These effects appear to be particularly significant when plants are exposed to neonicotinoids applied to soybean seeds.

The cotton agroecosystem is one of the most intensely managed, economically and culturally important fiber crops worldwide, including in the United States of America (U.S.), China, India, Pakistan, and Brazil. The composition and configuration of crop species and semi-natural habitat can have significant effects on ecosystem services such as pollination. Here, we investigated the local-scale effect of crop and semi-natural habitat configuration in a large field (>200 ha in size) cotton agroecosystem on the diversity and abundance of native bees. The interfaces sampled included cotton grown next to cotton, sorghum or semi-natural habitat along with a natural habitat comparator. Collections of native bees across interface types revealed 32 species in 13 genera across 3 families. Average species richness metrics ranged between 20.5 and 30.5, with the highest (30.5) at the interface of cotton and semi-natural habitat. The most abundant species was Melissodes tepaneca Cresson (>4000 individuals, ~75% of bees collected) with a higher number of individuals found in all cotton–crop interfaces compared to the cotton interface with semi-natural habitat or natural habitat alone. It was also found that interface type had a significant effect on the native bee communities. Communities of native bees in the cotton–crop interfaces tended to be more consistent in species richness and abundance. While cotton grown next to semi-natural habitat had higher species richness, the number of bees collected varied. These data suggest that native bee communities persist in large-field cotton agroecosystems. Selected species dominate (i.e., M. tepaneca) and thrive in this large-field cotton system where cotton–crop interfaces are key local landscape features. These data have implications for potential pollination benefits to cotton production. The findings also contribute to a discussion regarding the role of large-field commercial cotton growing systems in conserving native bees.

Los polinizadores para el cultivo de fibra de algodón están infrautilizados a pesar de la evidencia de que la polinización cruzada puede aumentar los rendimientos. Además, la investigación existente ignora en gran medida el potencial de los insectos distintos a las abejas (Hymenoptera: Apoidea: Anthophilia) para proporcionar servicios de polinización para el algodón. Observamos chinches de plantas, saltahojas del algodón, Pseudatomoscelis seriatus (Reuter) (Hemiptera: Miridae), visitando flores de algodón americano (upland), Gossypium hirsutum L. (Malvaceae) y llevando granos de polen de algodón sobre sus cuerpos. Presumimos que los saltahojas podrían contribuir a la polinización cruzada del algodón mientras se alimentan entre las flores. Para probar esta hipótesis, examinamos la frecuencia de visitas de flores de P. seriatus, la carga de polen de algodón, la dispersión de análogos de polen y la capacidad de polinización cruzada. Encontramos que los saltamontes del algodón visitaron el 21% de las flores observadas en nuestro sitio de campo y que depositaron un análogo de polen en el 12,5% de las flores accesibles en una jaula de campo. Sin embargo, es probable que los saltahojas de algodón individualmente sean demasiado pequeños para transportar suficientes granos para fertilizar las flores de algodón autoestériles, porque los saltahojas de algodón recolectados en el campo transportaban aproximadamente 25 granos de polen por insecto, que es menos de lo que se necesita para que las flores de algodón produzcan frutos. En general, encontramos que los saltahojas del algodón no pudieron estimular el desarrollo del fruto del algodón en flores autoestériles. Sin embargo, predecimos que los saltahojas del algodón pueden contribuir a la polinización cruzada del algodón dentro de una comunidad de polinizadores, y que pueden polinizar sus plantas hospedantes silvestres que tienen flores más pequeñas o agrupadas. Alentamos a los investigadores a continuar investigando polinizadores que no sean abejas en ecosistemas silvestres y agroecosistemas.

Robert F. Denno was widely recognized as one of the leading insect ecologists in the world. He made major contributions to the study of plant-insect interactions, dispersal, interspecific competition, predator-prey interactions, and food web dynamics. He was especially well known for his detailed and comprehensive study of the arthropods that inhabit salt marshes. Denno promoted a research approach that included detailed knowledge of the natural history of the study system, meticulous experiments that often pushed logistical possibilities, and a focus on important ecological questions of the day. He was an enthusiastic collaborator and excellent mentor who invested incredible amounts of time and energy in the training and placement of graduate students and postdoctoral associates. As a result, Denno's legacy will continue to shape the field of insect ecology for generations to come.